Imaging asteroids: Some lessons learned from the Viking investigation of Phobos and Deimos

Specific experiences from the study of Phobos and Deimos during the Viking mission are used to formulate three basic goals for imaging studies of asteroids. These are: (1) the highest possible resolution; (2) complete coverage of the surface; and (3) data over a wide range of phase angles

The physical meaning of phase coefficients

Asteroid surface properties determined by photometric measurements of phase curve between 10 and 30 de

Partial discharges in the transformers due to induced voltages

The supplement furnishes a theoretical proof containing the experimentally determined advantage for the connection of capacitance C sub 0 between the insulated frame and ground according to the arrangement presented in the article

Photometry and polarimetry

A review of available information on the photometry, polarimetry, and narrow band spectrophotometry of Titan discusses five major categories: (1) brightness and color as a function of orbital position; (2) brightness and color as a function of solar phase angle; (3) geometric and bond albedo; (4) reflectance as a function of wavelength; and (5) polarization as a function of solar phase angle. It is concluded that a Saturn-like cloud model may be required to explain the sum of polarimetric and photometric observations

Necessary stochastic maximum principle for dissipative systems on infinite time horizon

We develop a necessary stochastic maximum principle for a finite-dimensional stochastic control problem in infinite horizon under a polynomial growth and joint monotonicity assumption on the coefficients. The second assumption generalizes the usual one in the sense that it is formulated as a joint condition for the drift and the diffusion term. The main difficulties concern the construction of the first and second order adjoint processes by solving backward equations on an unbounded time interval. The first adjoint process is characterized as a solution to a backward SDE, which is well-posed thanks to a duality argument. The second one can be defined via another duality relation written in terms of the Hamiltonian of the system and linearized state equation. Some known models verifying the joint monotonicity assumption are discussed as well

Participation in the Mars data analysis program: Global and regional studies of wind-indicators on the surface of Mars

Global and regional patterns on Mars were inferred from surface aeolian features, such as wind streaks and dune deposits, which were visible in Viking Orbiter images. Precise measurements of the dimensions of topographic obstacles, i.e., craters, hills, ridges, on Mars as well as their associated wind streaks were used to determine the aerodynamic shape of an obstacle affects near surface airflow. A classification of Martian wind streaks was developed on the basis of albedo contrast and the presence or absence of either topographic obstacles or sediment deposits at the point of origin of the wind streaks. It was concluded that local meteorological conditions, such as the stability of the atmospheric boundary layer, play a major role in determining why some Martian craters produce depositional wind streaks while others produce erosional ones

Martian ionosphere - A component due to solar protons

Component of Mars ionosphere due to solar proton

The photometric roughness of Mimas

Voyager imaging observations of Mimas lie between 6 degrees and 132 degrees in phase angle and provide sufficient data with which to model such surface characteristics as large-scale roughness and directional scattering properties. Multiple scattering dominates the photometric behavior of the bright icy surface of Mimas, which has been shown to be moderately backscattering. Researchers analyzed disk-integrated and disk-resolved Voyager clear filter photometric using a modified version of Hapke's (1986) equation which accommodates anisotropic multiple scattering

Photometric properties of lunar terrains derived from Hapke's equation

Hapke's bidirectional reflectance equations provide the most rigorous available description of photometric behavior in terms of physically meaningful parameters. The primary objective of this study was to derive Hapke parameters for the lunar surface from both disk-integrated and disk-resolved photometric data. Hapke's equation was fit to the disk-integrated phase curves and disk-resolved data for dark, average, and bright terrain classes using an iterative, nonlinear least squares algorithm described by Helfenstein. Parameters were initially determined from the disk-integrated data, and the result was applied as a first guess to the iterative solution of parameters for individual terrain classes. Plots are presented of the disk-resolved data normalized to corresponding brightnesses predicted from the disk-integrated solution under the same illumination and viewing geometries. Systematic trends in disk-resolved parameters can be identified. Values for single scattering albedo (w) of the dominantly anorthositic average and bright terrains are significantly larger than the value for the basaltic dark terrains (mare). Values for surge brightness parameters, particle phase function, and average topographic slope angle are also discussed

Voyager observations of 1985U1

Of the 10 small Uranian satellites, 1985U1 is the largest and the only one for which a resolved image was obtained by Voyager 2. In terms of albedo, the other nine satellites seem to be similar. Thus the single image of 1985U1 is important in suggesting what these other objects may be like. Size, shape, surface features, and photometry are examined